It was a Friday afternoon like any other. I ate lunch, dropped off my dry cleaning, then stopped by my local Target to pick up some prescriptions.But on the way to the counter I noticed a man in a black coat, wearing a backpack bearing a sign: “In need of a kidney for my wife, B+. 917-442-6202.”Unsure what to say, I quickly snapped a photo. And then he was gone. Although I generally hate posting pictures of people online without getting their approval, I decided to share the image on Twitter since his face wasn’t in it — and because the message was so important.